1. Field of the Invention
The present invention relates to a substrate supporting member on which a substrate of a semiconductor wafer or the like is placed.
2. Description of Related Art
In a manufacturing process of semiconductor devices, various types of substrate supporting members on which substrates such as semiconductor wafers are placed have been used, for example, a ceramic heater, an electrostatic chuck, a hot electrostatic chuck, and the like.
The ceramic heater, electrostatic chuck, or the like includes a linear, plate-shaped or film shaped electrode embedded in a ceramic body having a disk shape in accordance with the shape of semiconductor wafers. The electrode of the ceramic heater is used as a heating element which raises substrate temperature to a predetermined temperature. The electrode of the electrostatic chuck is used to produce Coulomb force or Johnsen-Rabek force which attracts and fixes a semiconductor wafer onto the substrate supporting member.
Recently, as for an etching process in the manufacturing process of semiconductor devices, for the purpose of improving an etching selectivity and an aspect ratio of etching shape and the like, a so-called low-temperature etching process is proposed, which performs etching while cooling semiconductor wafers. In addition to such an etching process, processes requiring cooling of a semiconductor wafer placed on the substrate supporting member are increasing in various types of thin film processing or characteristic evaluation of substrates. Moreover, when the substrate supporting member is used in a process at high temperature, it is desired that the substrate supporting member is equipped with a cooling function in order to reduce the substrate temperature to the room temperature for a shorter time and control an in-plane temperature distribution of the semiconductor wafer in the high-temperature process.
To address such a need, a substrate supporting member is proposed in which a base body composed of a composite material of porous ceramic and filler metal is brazed using a brazing material to a ceramic body constituting a substrate supporting section of the substrate supporting member and is used as a heat sink (Japanese Patent Laid-open Publication No. 11-163109). The composite material has a thermal expansion coefficient lower than that of a metallic member and has good workability.
Moreover, a method of manufacturing a substrate supporting member is proposed in which the base body and ceramic body are pressure-welded (Japanese Patent Laid-open Publication 2005-101108).
In the manufacturing process of semiconductor devices, the substrate supporting member is provided in a processing chamber in which the atmosphere (gas concentration, gas pressure, gas temperature, and the like) can be controlled in a semiconductor device manufacturing apparatus. A substrate placed on this substrate supporting member is subjected to processing such as etching or film formation in a predetermined atmosphere of the processing chamber.
The base body of this substrate supporting member is made of the composite material of porous ceramic and filler metal as described above, in which all the pores of the porous ceramic are not filled with metal and a few pores remain unfilled. When the processing chamber is highly vacuumed for processing such as etching or film formation, accordingly, gas flows into the processing chamber from the outside through the pores remaining in the base body even if the processing chamber is sealed to be airtight in the periphery of the base body. This sometimes prevents the processing chamber from ensuring sufficient. sealing performance.
Moreover, the sealing in the periphery of the base body in the processing chamber is performed by sealing means such as an O-ring. The pores remaining in the base body are exposed in the surface. Accordingly, some pores communicate between the inside and outside in the sealing surface of the O-ring or the like even if the pores do not communicate with each other within the base body. Furthermore, the difference in thermal expansion coefficient between the ceramic body and base body of the substrate supporting member sometimes causes warp of the base body of the substrate supporting member. The warp of the base body might cause degradation in adhesion of the seal portion and might inversely affect the sealing by the sealing means in the periphery of the base body.
When air flows into the processing chamber from the outside during the processing of the substrate, processing conditions of the substrate fluctuate, making it difficult to perform good film formation and etching.
The present invention is advantageous in solving the aforementioned problems, and an object of the present invention is to provide a substrate supporting member which is capable of maintaining high vacuum in the processing chamber.